GeographyCBSE Class 12 · The World Population: Distribution, Density and Growth

Components of Population Change (Class 12 Geography, Chapter 2)

Updated 15 October 2026 · Fact-checked

Population changes through three components: births, deaths and migration. Births are measured by the crude birth rate and deaths by the crude death rate, both per thousand people. Natural growth is births minus deaths; actual growth also adds in-migration and subtracts out-migration. Migration is driven by push factors at the origin and pull factors at the destination.

Natural growth uses only births and deaths; actual growth also adds in-migration and subtracts out-migration, driven by push and pull factors.

Illustration drawn for QuestionBuddy.

Understand Components of Population Change

Why this topic matters. Formulas (CBR, CDR, natural and actual growth), push-pull factors and data-based items on birth and death rates come up as 1-mark MCQs, case-based items and 5-mark 'define migration and differentiate' questions.

1. Population growth: the basic terms.

Population change or growth: change in the number of people in an area between two points of time; it may be positive or negative, in absolute numbers or as a percentage.
Growth rate: the change expressed as a percentage.
Natural growth = Births − Deaths.
Actual growth = Births − Deaths + In-migration − Out-migration.
Positive growth: birth rate exceeds death rate, or people migrate permanently into the region.
Negative growth: birth rate falls below death rate, or people migrate out to other countries.
Population change is an indicator of economic development, social upliftment and the historical and cultural background of a region.

2. Births: crude birth rate (CBR). Live births in a year per thousand people:

$CBR = \frac{B}{P} \times 1000$ , where B = live births in the year and P = estimated mid-year population.

3. Deaths: crude death rate (CDR). Deaths in a year per thousand people:

$CDR = \frac{D}{P} \times 1000$ , where D = deaths in the year and P = estimated mid-year population.

Population grows not only through more births but also through falling death rates.
Mortality depends on a region's demographic structure, social advancement and level of economic development.

4. Migration.

Place of origin (people leave; population falls) and place of destination (people arrive; population rises).
Immigrants move into a new place; emigrants move out of a place. The same person is an emigrant for the origin and an immigrant for the destination.
Migration may be permanent, temporary or seasonal, and rural-rural, rural-urban, urban-urban or urban-rural.
It can be seen as a spontaneous effort to balance population and resources.

5. Push and pull factors.

Push factors (origin less attractive)	Pull factors (destination more attractive)
Unemployment	Better job opportunities
Poor living conditions	Better living conditions
Political turmoil	Peace and stability
Unpleasant climate	Pleasant climate
Natural disasters, epidemics	Security of life and property
Socio-economic backwardness

6. Worked numerical (our own data). A town's mid-year population is 2,40,000. In the year there were 4,560 live births, 1,680 deaths, 1,500 in-migrants and 900 out-migrants.

CBR = 4,560 ÷ 2,40,000 × 1000 = 19 per thousand.
CDR = 1,680 ÷ 2,40,000 × 1000 = 7 per thousand.
Natural growth = 4,560 − 1,680 = 2,880.
Actual growth = 2,880 + 1,500 − 900 = 3,480.
Natural growth rate = 19 − 7 = 12 per thousand (1.2 per cent).

7. Long-term change. NCERT notes that human population grew more than ten times in the past 500 years and four times in the twentieth century alone.

Components of Population Change: key facts

Crude birth rate: $CBR = \frac{B}{P} \times 1000$; B = live births in the year; P = estimated mid-year population.
Crude death rate: $CDR = \frac{D}{P} \times 1000$; D = deaths in the year; P = estimated mid-year population.
Natural growth: $Natural growth = Births - Deaths$; As a rate: CBR − CDR, per thousand.
Actual growth: $Actual growth = Births - Deaths + In-migration - Out-migration$; Migration is the only difference from natural growth.
Migration vocabulary: Immigrant moves into a place
Emigrant moves out of a place
Place of origin population falls
Place of destination population rises; One person is both, seen from two places.

Immigrant	moves into a place
Emigrant	moves out of a place
Place of origin	population falls
Place of destination	population rises

How to answer Components of Population Change questions

Expect MCQs on the three components and push-pull factors, data-based items asking which period had the highest natural growth, and 5-mark questions that ask you to define migration and contrast push and pull factors.

1For a rate question, write the formula first, then substitute with mid-year population.
2For 'highest natural growth' in a table, subtract CDR from CBR for every row; do not pick the highest CBR.
3For migration, define it with origin and destination, then classify by duration and direction.
4In push-pull answers, pair each push factor with its matching pull factor.
5State units: per thousand for rates, number of persons for growth.

Components of Population Change in real life

The idea, met in an everyday situation. Answer the question in your own words, then compare with the model answer. The one-line hook is what to remember.

Push and pull factors

Suppose a young man from a drought-hit village, where the family farm gives very low returns, moves to a city that offers factory jobs and evening training courses.

Identify one push factor and two pull factors in this move, and say whether he is an immigrant or emigrant.

Try it first, then show the solutionSolution

Push factors make the origin less attractive: drought and low farm income (unemployment, poor living conditions).
Pull factors make the destination more attractive: jobs and training.
He is an emigrant from the village and an immigrant in the city.

Answer: Push: drought and low farm returns. Pull: better job opportunities and training. He is an emigrant for the village and an immigrant for the city.

Memory hook: Push from home, pull to the city: one journey, two labels.

Tricks to remember Components of Population Change

Short memory aids. Say each one aloud once, then use it on a question the same day.

BDM: Births, Deaths, Migration
'Babies, Departures, Moves': the three ways a population changes.
Use it when: Naming the components.
IN-to, EX-it
Immigrant comes IN; Emigrant EXits (E for exit).
Use it when: Immigration vs emigration.
Natural is closed, actual is open
Natural growth treats the area like a closed box (births − deaths); actual growth opens the doors to migrants.
Use it when: Choosing the right growth formula.

Components of Population Change: solved examples

Ordered from board level to HOTS. Try each one before you open the solution.

Example 1: Components of change · 1 mark · MCQBoard level

A census officer wants to explain why the population of a hill town changed between 2015 and 2025. Which set of information must she collect?
(A) Area of the town, number of houses and literacy rate
(B) Number of births, number of deaths and the number of people who moved in and out
(C) Sex ratio, age structure and density
(D) Number of schools, hospitals and roads

Try it first, then show the solutionSolution

Population can change only through births, deaths or migration, the three components of population change (1 mark).

Answer: (B) Number of births, number of deaths and the number of people who moved in and out

Example 2: Highest natural growth from data · 1 mark · MCQHarder board level

A country recorded these rates (per thousand):
Decade P: CBR 34.0, CDR 14.5
Decade Q: CBR 30.5, CDR 9.0
Decade R: CBR 27.0, CDR 8.0
Decade S: CBR 22.0, CDR 7.5
Which decade registered the highest natural growth rate?
(A) P
(B) Q
(C) R
(D) S

Try it first, then show the solutionSolution

Natural growth = CBR − CDR: P 19.5, Q 21.5, R 19.0, S 14.5; the highest is Q (1 mark).

Answer: (B) Q

Example 3: Calculating CBR and CDR · 3 marks · Short answerBoard level

A district's estimated mid-year population is 1,50,000. During the year it had 3,150 live births and 2,100 deaths. Calculate (i) CBR, (ii) CDR and (iii) natural growth. (3 marks)

Try it first, then show the solutionSolution

CBR = 3,150 ÷ 1,50,000 × 1000 = 21 per thousand (1 mark).
CDR = 2,100 ÷ 1,50,000 × 1000 = 14 per thousand (1 mark).
Natural growth = 3,150 − 2,100 = 1,050 persons, i.e. 7 per thousand (1 mark).

Answer: (i) CBR = 21 per thousand. (ii) CDR = 14 per thousand. (iii) Natural growth = 1,050 persons, a natural growth rate of 7 per thousand.

Example 4: Natural vs actual growth · 3 marks · Short answerHarder board level

Distinguish between natural growth and actual growth of population. Why can a city have negative natural growth but positive actual growth? (3 marks)

Try it first, then show the solutionSolution

Natural growth = births − deaths (1 mark).
Actual growth = births − deaths + in-migration − out-migration (1 mark).
If deaths exceed births but in-migrants far outnumber out-migrants, actual growth is positive (1 mark).

Answer: Natural growth is the difference between births and deaths in an area between two points of time. Actual growth also includes migration: births minus deaths plus in-migration minus out-migration. A city with an ageing population may record more deaths than births, giving negative natural growth, yet if it attracts many migrants for jobs, in-migration outweighs both the natural decrease and out-migration, so the actual population rises.

Example 5: Long answer: migration · 5 marks · Long answerHarder board level

Define migration. Differentiate between push and pull factors of migration with examples. (5 marks)

Try it first, then show the solutionSolution

Definition: movement of people from a place of origin to a place of destination; origin loses and destination gains population (1 mark).
Types: permanent, temporary or seasonal; rural-rural, rural-urban, urban-urban, urban-rural (1 mark).
Push factors make the origin less attractive: unemployment, poor living conditions, political turmoil, unpleasant climate, disasters, epidemics, backwardness (1.5 marks).
Pull factors make the destination more attractive: better jobs and living conditions, peace and stability, security of life and property, pleasant climate (1.5 marks).

Answer: Migration is the movement of people from one place, the place of origin, to another, the place of destination. The origin loses population and the destination gains it. Migration may be permanent, temporary or seasonal, and may be rural to rural, rural to urban, urban to urban or urban to rural. It can be seen as an attempt to balance population and resources.

Push factors operate at the origin and make it seem less attractive: lack of jobs, poor living conditions, political turmoil, a harsh climate, disasters and epidemics, and general socio-economic backwardness. For example, repeated crop failure may push a farmer out of a village.

Pull factors operate at the destination and make it seem better than the origin: more jobs, better living conditions, peace, stability, safety of life and property, and a pleasant climate. For example, factory jobs and schools may pull the same farmer to a city. People usually move when push and pull factors act together.

Example 6: Case-based: an emigrant's choice · 3 marks · Case-basedHOTS / competency

Read the case: 'Arjun, 28, lives in a hill village where landslides blocked the only road three times last year. His family's small orchard earns little. A cousin in a coastal city tells him about steady jobs in a port and safe housing.'
(i) Identify two push factors. (1)
(ii) Identify two pull factors. (1)
(iii) If Arjun moves, explain how the populations of the village and the city change and name the component involved. (1)

Try it first, then show the solutionSolution

(i) Natural disasters (landslides) and low income/poor living conditions (1 mark).
(ii) Better job opportunities and security of life and property (safe housing) (1 mark).
(iii) The village (origin) loses a person and the city (destination) gains one: migration (1 mark).

Answer: (i) Landslides (natural disasters) and low earnings from the orchard. (ii) Steady port jobs and safe housing. (iii) The village's population falls and the city's rises; the component is migration (he is an emigrant from the village and an immigrant in the city).

Where students lose marks in Components of Population Change

The slips examiners see most often, and what to write instead.

Mistake: Forgetting × 1000 in CBR and CDR
Students give a decimal.
Wrong working
CBR = 3,150 ÷ 1,50,000 = 0.021.
Right working
CBR = 3,150 ÷ 1,50,000 × 1000 = 21 per thousand.
Do this: Rates are per thousand: multiply by 1000.
Usually costs: 1 mark.
Mistake: Picking the highest CBR as the highest natural growth
Reading only one column.
Wrong working
Decade P has the highest growth because its CBR is 34.
Right working
Natural growth is CBR − CDR; Q has the largest gap (21.5).
Do this: Subtract for every row before choosing.
Usually costs: 1 mark.
Mistake: Mixing immigrant and emigrant
Similar words.
Wrong working
A person leaving a village is an immigrant of the village.
Right working
He is an emigrant from the village and an immigrant in the city.
Do this: IN-to, EX-it.
Usually costs: 1 mark.
Mistake: Listing pull factors as push factors
Not checking which place the factor describes.
Wrong working
Push factors: better jobs, peace.
Right working
Push: unemployment, turmoil (at origin). Pull: better jobs, peace (at destination).
Do this: Ask: does it describe home or the new place?
Usually costs: Up to 2 marks in a 5-mark answer.

Exam tips

Asked in: 2024 board paper 64/1/1 Q16 (1 mark, the three components); 2023 board papers 64/1/1 Q9 and 64/4/1 Q2 (1 mark each, push factors); 2025 board paper 64/7/1 Q27(b) (5 marks, define migration, push and pull factors); 2026-27 sample paper Q9 (1 mark, highest natural growth from a CBR-CDR table) and Q17 (1 mark, reasons for emigration in a case). The answers on this page are our own.
Always write the formula before the numbers; it earns a step mark even if arithmetic slips.
For push-pull answers, a two-column table is quick and clear.
Use the term 'mid-year population' for P; it shows precision.

Practice questions on Components of Population Change

Write each answer on paper first. Open the hint only if you are stuck, and the answer only when you have finished.

Q1 · 1 mark · MCQBoard level
Which one of the following is a push factor of migration?
(A) Peace and stability
(B) Better job opportunities
(C) Epidemics
(D) Pleasant climate
Hint
Push makes the origin unattractive.
Answer
(C) Epidemics.
Q2 · 1 mark · MCQHarder board level
A town with a mid-year population of 80,000 recorded 1,440 live births. Its CBR is:
(A) 1.8 per thousand
(B) 18 per thousand
(C) 180 per thousand
(D) 55.5 per thousand
Hint
Births ÷ population × 1000.
Answer
(B) 18 per thousand: 1,440 ÷ 80,000 × 1000 = 18.
Q3 · 2 marks · Very short answerBoard level
Two towns have the same number of deaths in a year, 900 each. Town X has a mid-year population of 60,000 and town Y of 1,00,000. Which town has the higher crude death rate? Show working. (2 marks)
Hint
CDR = D ÷ P × 1000; same D, different P.
Answer
CDR of X = 900 ÷ 60,000 × 1000 = 15 per thousand. CDR of Y = 900 ÷ 1,00,000 × 1000 = 9 per thousand. Town X has the higher crude death rate, because the same number of deaths is spread over fewer people.
Q4 · 1 mark · Assertion-reasonHarder board level
Assertion (A): Population can grow even when the birth rate does not rise.
Reason (R): A decline in the death rate also increases population.
(A) Both (A) and (R) are true and (R) is the correct explanation of (A).
(B) Both (A) and (R) are true but (R) is not the correct explanation of (A).
(C) (A) is true but (R) is false.
(D) (A) is false but (R) is true.
Hint
Death rate plays an active role.
Answer
(A) Both are true and R explains A.
Q5 · 3 marks · Short answerHarder board level
A region had 12,000 births, 5,000 deaths, 2,000 in-migrants and 6,000 out-migrants in a year. Find natural growth and actual growth, and comment. (3 marks)
Hint
Out-migration is subtracted.
Answer
Natural growth = 12,000 − 5,000 = 7,000. Actual growth = 7,000 + 2,000 − 6,000 = 3,000. Heavy out-migration has cut the actual increase to less than half of the natural increase, a sign that the region pushes people out (for example, through lack of jobs).
Q6 · 3 marks · Short answerHOTS / competency
Why does NCERT say migration may be seen as a spontaneous effort to balance population and resources? Explain with a hypothetical example. (3 marks)
Hint
Too many people, too few jobs in one place; the opposite elsewhere.
Answer
Where population is large relative to land, jobs or water, people move to places where resources or opportunities are more plentiful. Suppose a village's farms cannot support all its young people while a nearby industrial town is short of workers; migration from village to town reduces pressure at the origin and fills the labour gap at the destination. No authority plans it; people move on their own, so it is a spontaneous balancing.
Q7 · 5 marks · Long answerHOTS / competency
"Population change is an important indicator of a region's development." Examine the statement using births, deaths and migration. (5 marks)
Hint
Mortality depends on social advancement; migration follows opportunity.
Answer
NCERT calls population change an indicator of economic development, social upliftment and the historical and cultural background of a region. Births: high birth rates usually go with agrarian societies where large families are an asset, while low birth rates appear where people are urban, literate and plan family size. Deaths: mortality rates depend on the demographic structure, social advancement and economic development of a region; better sanitation and health care lower the death rate. Migration: people move out of areas with unemployment, poor living conditions or unrest and into areas with jobs, stability and security, so net in-migration often marks a prospering region and net out-migration a lagging one. Hence the pattern of change in an area reveals its level of development, though each component should be read together, not alone.

Test your recall

Answer in your head or on paper first, then open the card. Pulling an answer out of memory makes it stick far better than re-reading.

1.What is P in the CBR formula?Show answer
The estimated mid-year population of the area.
2.Write the formula for actual growth.Show answer
Births − deaths + in-migration − out-migration.
3.What is the place a migrant moves to called?Show answer
Place of destination.
4.Name three push factors.Show answer
Any three: unemployment, poor living conditions, political turmoil, unpleasant climate, natural disasters, epidemics, socio-economic backwardness.
5.By how many times did population increase in the twentieth century?Show answer
Four times.

Components of Population Change: frequently asked questions

What are the three components of population change?

Births, deaths and migration.

How is crude birth rate calculated?

CBR = (live births in the year ÷ estimated mid-year population) × 1000, giving births per thousand people.

What is the difference between natural and actual growth?

Natural growth is births minus deaths. Actual growth also adds in-migration and subtracts out-migration.

What are push and pull factors?

Push factors make the place of origin less attractive (unemployment, unrest, disasters); pull factors make the destination more attractive (jobs, peace, security, pleasant climate).